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"\r\nA pointer works by pointing to a specified valid address. Yet, it doesn’t necessarily point to valid elements. These cases are often called invalid pointers.  \r\n\r\n\r\nIn C++, the free() function often employs the malloc, calloc, and realloc functions to deallocate a memory block, which is previously allocated. This way, you can make further allocations. \r\n\r\n\r\nThe function doesn’t change the pointer’s value so that it navigates to the same memory location. However, what if you get the free() invalid pointer error in C++? How to fix the problem? The following article will reveal the answer. \r\n\r\n\r\nHow To Fix Free Invalid Pointer Error In C++\r\n\r\n\r\n\r\nThere are two main ways to fix the free invalid pointer error in C++. \r\n\r\n\r\nMethod 1: Free Pointer With Non-Dynamic Memory Locations\r\n\r\n\r\n\r\nThe main function of the free() option should be deallocating the returned pointers’ memory from the calloc, realloc, and malloc options. \r\n\r\n\r\nThe example will focus on the char* pointer gets a value of the malloc call and then comes in the else block. In this case, such a pointer is still assigned with a string.  \r\n\r\n\r\nFor this reason, the variable c_str navigates you to a non-dynamic memory location. The free option will refuse this variable. Due to this execution, when the next program runs the free function, it will likely get aborted and catch the free(): invalid pointer error. \r\n\r\n\r\nTo avoid this issue, you should not use various addresses to assign this pointer to different dynamic memory locations. You can do it if all variables point to the same location. \r\n\r\n\r\nMake sure to call the free function when your pointers reach heap memory. \r\n\r\n\r\n\r\n#include &lt;stdlib.h&gt;\r\n\r\n#include &lt;string.h&gt;\r\n\r\n#include &lt;stdio.h&gt;\r\n\r\nint main(int argc, const char *argv[]) {\r\n\r\n    char *c_str = NULL;\r\n\r\n    size_t len;\r\n\r\n    if (argc != 2) {\r\n\r\n        printf(\"Usage: ./program string\\n\");\r\n\r\n        exit(EXIT_FAILURE);\r\n\r\n    }\r\n\r\n    if ((len = strlen(argv[1])) &gt;= 4) {\r\n\r\n        c_str = (char *)malloc(len);\r\n\r\n        if (!c_str) {\r\n\r\n            perror(\"malloc\");\r\n\r\n        }\r\n\r\n        strcpy(c_str, argv[1]);\r\n\r\n        printf(\"%s\\n\", c_str);\r\n\r\n    } else {\r\n\r\n        c_str = \"Some Literal String\";\r\n\r\n        printf(\"%s\\n\", c_str);\r\n\r\n    }\r\n\r\n    free(c_str);\r\n\r\n    exit(EXIT_SUCCESS);\r\n\r\n}\r\n\r\n\r\n\r\n\r\nMethod 2: Don’t Free Pointers Which Are Freed\r\n\r\n\r\n\r\nAnother reason behind the free invalid pointer error is calling the option on the already freed pointers. This is because you reassign various pointer variables to one original memory region. \r\n\r\n\r\n\r\n#include &lt;stdlib.h&gt;\r\n\r\n#include &lt;string.h&gt;\r\n\r\n#include &lt;stdio.h&gt;\r\n\r\nint main(int argc, const char *argv[]) {\r\n\r\n    char *c_str = NULL;\r\n\r\n    size_t len;\r\n\r\n    if (argc != 2) {\r\n\r\n        printf(\"Usage: ./program string\\n\");\r\n\r\n        exit(EXIT_FAILURE);\r\n\r\n    }\r\n\r\n    char *s = NULL;\r\n\r\n    if ((len = strlen(argv[1])) &gt;= 4) {\r\n\r\n        c_str = (char *)malloc(len);\r\n\r\n        s = c_str;\r\n\r\n        if (!c_str) {\r\n\r\n            perror(\"malloc\");\r\n\r\n        }\r\n\r\n        strcpy(c_str, argv[1]);\r\n\r\n        printf(\"%s\\n\", c_str);\r\n\r\n        free(c_str);\r\n\r\n    } else {\r\n\r\n        c_str = \"Some Literal String\";\r\n\r\n        printf(\"%s\\n\", c_str);\r\n\r\n    }\r\n\r\n    free(s);\r\n\r\n    exit(EXIT_SUCCESS);\r\n\r\n}\r\n\r\n\r\n\r\n\r\nThe above example involves solving the problem in a short and single file program. Thus, it would be easier to diagnose and fix the error. In the real scenario, you tend to get a larger codebase, which is difficult to track without an external inspector program. \r\n\r\n\r\nConclusion\r\n\r\n\r\n\r\nYour program is running smoothly when there is an error popping up and telling free: invalid pointer. What is the problem? How to fix the free invalid pointer error? \r\n\r\n\r\nThe article has introduced two methods to fix the free invalid pointer error. "
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